Adhesive compositions are used to affix (bond) glass (windows) into buildings and vehicles, see Rizk, U.S. Pat. No. 4,780,520; Bhat, U.S. Pat. No. 5,976,305; Hsieh et al, U.S. Pat. No. 6,015,475 and Zhou, U.S. Pat. No. 6,709,539, all incorporated herein by reference. In automobile factories windows are installed using robots and computer controlled processing. This facilitates the use of a variety of high performance adhesives used on a variety of automobiles, for instance nonconductive adhesives and high modulus adhesives. Further, new vehicles are not driven a significant distance for several days after window installation, and thus the speed of cure is not a significant issue. Conversely, when a vehicle needs a window replaced, it is often performed in a remote location by an installer working from a vehicle. In this environment, speed of cure is important as the vehicle owner desires to drive the vehicle away as soon as possible after installation on the window. Adhesives useful in replacing windows for vehicles which facilitate fast drive away times are known see Bhat, U.S. Pat. No. 5,976,305 and Zhou, U.S. Pat. No. 6,709,539. The introduction of various high performance adhesive compositions used for installing windows in automobile factories presents a problem for replacement window installers. First adhesives that meet all the varied performance requirements are not available in the market place. Second, it is difficult to formulate many high performance adhesive compositions to allow rapid drive away times, such as one hour and more preferably 30 minutes. Thus, a replacement window installer often has to carry a variety of adhesives so that the installer can match the adhesive to the properties of the original adhesive. It is also difficult to formulate a high performance adhesive that does not sag, that is, lose the shape of the adhesive bead applied to the vehicle or the glass.
Adhesives have been developed which provide good initial green strength that allows the adhesive to hold the glass in place without additional fixturing to hold the glass in place. This is achieved through the inclusion of crystalline polyesters in the adhesive. These adhesives have hot melt properties that require that the adhesive be melted and applied hot. As the adhesive cools the polyester portion crystallizes and provides initial green strength to hold the glass in place, see Proebster U.S. Pat. No. 5,747,581, incorporated herein by reference. The problem with these adhesives is that they require heat to apply and the use of complex equipment including a heater for their use. The initial green strength provided is not sufficient for rapid drive away time. In the replacement glass industry segment rapid strength development is necessary to allow safe rapid drive away times. Because of the use of hot melt adhesives in the automobile window replacement market, many installers insist on heating adhesives prior to applying the adhesive to the window or the window flange. Many adhesives when heated demonstrate sagging, that is the deformation as the result of gravitational forces. This deformation if severe enough can interfere in the proper installation and sealing of the window into the vehicle.
Several approaches to providing non-conductive adhesives including using non-conductive carbon black in adhesive formulations are known, see commonly assigned patent application Ser. No. 10/921,635 filed Aug. 19, 2004 titled COMPOSITION USEFUL AS AN ADHESIVE FOR INSTALLING VEHICLE WINDOWS. WO 02/053671 discloses the use of low or non-oxidized carbon black with polycarbonate based polyols to achieve this objective. The problem with this technology is that low, conductive carbon black and polycarbonate polyols are significantly more expensive than standard grades of carbon black which are conductive.
Windows in buildings and vehicles are installed and replaced in a variety of environmental conditions. Many of the present adhesive compositions are limited with respect to the environmental conditions of application. As a result window installers often need to use different adhesives based on the environmental conditions.
What is needed is a composition which is useful as an adhesive for bonding glass into a structure which exhibits a variety of high performance properties (such as high modulus and nonconductive nature), exhibits fast safe drive away times when applied under a variety of conditions, fast strength development, can be applied without the need for heating the adhesive, can be applied under a wide range of environmental conditions, does not require expensive ingredients and does not sag when applied. Further, what is needed is an adhesive composition which does not sag when heated prior to application to temperatures of up to 80° C.